1. Field
The present disclosure relates generally to security in data processing systems, and more particularly, efficient transmission of cryptographic information in secure real time protocol.
2. Background
Real Time Protocol (RTP) is an Internet protocol standard for real time transmission of multimedia data. Today, RTP supports numerous multimedia applications including, by way of example, multicast and unicast network services. Multicast network services are usually associated with a multimedia transmission from a content provider to any number of distributed subscribers. Unicast network services are usually associated with a multimedia transmission from a content provider to a single subscriber. In either case, the subscriber can view the multimedia data in real time, or download the data for later viewing.
As the demand for multimedia applications continues to grow, the need for secured transport of multimedia content becomes more apparent. A new standard, called Secure Real Time Protocol (SRTP), has recently emerged in the telecommunications industry to address this need. SRTP can provide confidentiality, message authentication, and data integrity for RTP traffic. SRTP can also protect against active attacks such as replay attack and the like.
In SRPT, traffic is transported in packets. Namely, data to be transmitted is broken into packets. Each packet includes a header and payload. Using a same session key, the payload is encrypted at the transmitting end and decrypted at the receiving end. The session key is a short term key that is changed periodically, typically multiple times during a single multimedia broadcast. A master key is used to derive the session key in a cryptographically secure way. More particularly, a short term random number (SK_RAND), generated by the transmitting end and sent to the receiving end, is applied to a key derivation function at both ends using the master key to produce the session key. The master key is typically a long term key that remains valid for the subscription period of the multimedia subscriber.
The SRTP also includes an optional field called a Master Key Identifier (MKI). This field may be included in the SRPT header. The MKI may be used to identify the master key from which the session key(s) were derived and may be used for other key management. In multicast network services, such as broadcast systems, the SK-RAND and other information is carried by the MKI.
However, SRTP requires that the MKI information be sent with every packet, or none of the packets, thereby wasting valuable bandwidth. Accordingly, there is a need for a more efficient and/or effective way to send the MKI in SRTP.